Antimicrobial resin composition

ABSTRACT

The present invention provides a resin composition having excellent dispersibility, discoloration resistance and antimicrobial properties by blending a resin (A) with an antimicrobial agent (B) in which at least one kind of metal ion selected from the group consisting of silver, copper, zinc, and tin is supported on zeolite, and an antimicrobial agent (C) that includes a silver ion-containing phosphate as an active ingredient, or an antimicrobial agent (D) made of a soluble glass powder containing silver ion.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to antimicrobial resincompositions. More specifically, the present invention relates toantimicrobial resin compositions having excellent antimicrobialproperties and excellent dispersibility and discoloration resistance.

[0002] With recent increasing consciousness of cleanliness of consumersand consumer needs in the pursuance of high-value-added products, it hasbeen promoted to subject products to antimicrobial processing in variousfields, for example, stationery such as ball-point pens and erasers,miscellaneous goods of daily use including kitchenware such as cuttingboards and bathroom ware such as bathtubs, home electric appliances suchas telephone sets, rice cookers, and refrigerators, building materialssuch as floor materials and wall materials, and textile products such asbed sheets, pajamas, sanitary clothing, and curtains.

[0003] There are generally two kinds of methods for subjecting productsto antimicrobial processing. In one method, an antimicrobial agent isadded to resin and kneaded in the stage of manufacturing products suchas plastic molded articles, synthetic textiles and films. Theantimicrobial properties of the antimicrobial-processed productsobtained by this method last for a long time. In another method, theseproducts are coated with a coating agent containing an antimicrobialagent. The antimicrobial-processed products obtained by this method tendto lose their antimicrobial properties gradually because the coatedlayer is peeled off through use. Either method is appropriately selecteddepending on the materials of the commercial products, the manufacturingconditions of the commercial products, the required characteristics, andthe types of antimicrobial agents to be used.

[0004] On the one hand, antimicrobial agents are classified broadly intoorganic antimicrobial agents and inorganic antimicrobial agents. Organicantimicrobial agents raise health concerns and many of them do not havesufficient antimicrobial activity. On the other hand, inorganicantimicrobial agents employ metal ions, typically, silver ion and areexcellent in safety and antimicrobial activity. Accordingly, in general,for the above-described products, inorganic antimicrobial agents areused.

[0005] The antimicrobial activity of inorganic antimicrobial agentsemploying metal ions depends on the dissolution rate of the metal ionsthat are used. When inorganic antimicrobial agents employing metal ionsare blended into resin, the metal ions react with additives such ascatalyst residue, antioxidant, photostabilizer or the like in the resinand therefore degrade the antimicrobial activity. Moreover, the resin isdiscolored by light or heat.

[0006] In the case of resins molded by methods such as injectionmolding, extrusion molding or blow molding, antimicrobial agents aregenerally added to the resin in the stage of masterbatch molding, and itis necessary that antimicrobial agents are dispersed effectively intothe resin and on the surface of the resin in order to maximize theantimicrobial ability.

[0007] There is a demand for a resin composition that does not changeits color to yellowish-brown through light or heat and has excellentdispersibility in a resin and further provides significant antimicrobialproperties.

SUMMARY OF THE INVENTION

[0008] In order to solve the above problems, the inventors of thepresent invention conducted research, and found that by combiningspecific antimicrobial agents, drawbacks of each antimicrobial agent arecomplemented and each function is exhibited synergistically and theabove problems can be solved, thus achieving the present invention.

[0009] The present invention relates to an antimicrobial resincomposition, wherein a resin (A) is blended with an antimicrobial agent(B) in which at least one kind of metal ion selected from the groupconsisting of silver, copper, zinc and tin is supported on zeolite, andan antimicrobial agent (C) that includes a silver ion-containingphosphate as an active ingredient, or a soluble glass powder (D)containing silver ion.

[0010] In a preferable embodiment, 0.01 to 10 parts by weight of theantimicrobial agent (B) and 0.01 to 10 parts by weight of theantimicrobial agent (C) are blended with respect to 100 parts by weightof the resin (A).

[0011] In another preferable embodiment, 0.01 to 10 parts by weight ofthe antimicrobial agent (B) and 0.01 to 10 parts by weight of theantimicrobial agent (D) are blended with respect to 100 parts by weightof the resin (A).

[0012] In a preferable embodiment, the resin (A) is a thermoplasticresin. In a further preferable embodiment, this thermoplastic resin ispolyolefin.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] There is no particular limitation regarding the resin (A) used inthe present invention. Examples of the resin (A) include a thermoplasticresin, a thermosetting resin, and a reproduced or semi-syntheticpolymer. Examples of thermoplastic resins include polyolefin,polystyrene, polyamide, polyester, polyvinyl alcohol, polycarbonate,polyacetal, ABS resin, acrylic resin, fluorocarbon resin, polyurethaneelastomer, and polyester elastomer. Examples of thermosetting resinsinclude phenolic resin, urea resin, melamine resin, unsaturatedpolyester resin, epoxy resin, and urethane resin. Examples of theregenerated or semi-synthetic polymer include rayon, cupra, acetate, andtriacetate.

[0014] In particular, polyolefins contain a chlorine-compound (titaniumtetrachloride, titanium trichloride, etc.) derived from a Ziegler Nattacatalyst and additives containing chlorine (chlorinated paraffin,perchloro penta cyclodecane, and the like) such as flame retardant, andtherefore polyolefins are easily discolored by blending an antimicrobialagent. However, when the antimicrobial agent (B) and the antimicrobialagent (C) or (D) used in the present invention are blended with apolyolefin, discoloration is significantly inhibited and antimicrobialproperties are improved. Accordingly, polyolefin is preferable as aresin used in the present invention because of the remarkable effects asdescribed above.

[0015] There is no particular limitation regarding the polyolefin.Examples of polyolefins include a homopolymer of α-olefin such asethylene, propylene, butene-1, hexane-1, and 4-methyl pentene-1; acopolymer of ethylene and propylene or other α-olefins; or at least twokinds of copolymer of these α-olefins. Among these examples,polyethylene (for example, low density polyethylene, linear low densitypolyethylene, medium density polyethylene, high density polyethylene, orthe like) and polypropylene are preferable. The polypropylene is notlimited to homopolymer. A random copolymer or a block copolymer ofpropylene and other α-olefins containing 50 mol % or more, preferably 80mol % or more of propylene components may also be used. Examples ofcomonomers that can be copolymerized with propylene include ethylene andother α-olefins, and ethylene is particularly preferable.

[0016] In the antimicrobial agent (B) used in the present invention, atleast one kind of metal ion selected from the group consisting ofsilver, copper, zinc, and tin is supported on zeolite. Thisantimicrobial agent (B) is characterized in that its safety has beenconfirmed by the test regarding toxicity and impact on environment underthe US EPA guideline, and that the antimicrobial agent (B) is based onzeolite, and that it has a low hardness of 2 to 3 and contains crystalwater. Due to the characteristic of containing crystal water, theantimicrobial agent (B) has the advantage that it suppresses heat frombeing generated during kneading of the resin. On the other hand, it hasthe drawback that depolymerization occurs when it is kneaded intopolyester.

[0017] However, this drawback of the antimicrobial agent (B) is resolvedby mixing with an antimicrobial agent (C) or an antimicrobial agent (D),which will be described later, improving the antimicrobial activity.

[0018] Examples of the antimicrobial agent (B) used in the presentinvention include the antimicrobial agents described in JapaneseLaid-Open Patent Publication (Tokkai) No. 62-241832 and Japanese PatentPublication (Tokko) No. 63-28402. The average particle diameter of theantimicrobial agent (B) is preferably 0.2 to 10 μm, and more preferably2 to 5 μm. If the particle diameter is less than 0.2 μm or more than 10μm, the dispersibility of the antimicrobial agent (C) or theantimicrobial agent (D) is not improved. As a commercially availableproduct, for example, there is “BACTEKILLER (product name) manufacturedby Kanebo LTD.”

[0019] The antimicrobial agent (C) used in the present invention is anantimicrobial agent that includes a silver ion-containing phosphate asits active ingredient. An example of the antimicrobial agent (C) isdescribed in Japanese Patent Publication (Tokko) No. 6-10126. Apreferable antimicrobial agent (C) includes a compound expressed by thefollowing general formula as its active ingredient:

Ag_(x)H_(y)M₂(PO₄)₃

[0020] where A is an alkali metal, M is Zr, Ti or Sn, x, y, and z arepositive numbers smaller than 1, and x+y+z=1.

[0021] The antimicrobial agent (C) has the advantages that it causesdiscoloration of the resin to a smaller degree than the antimicrobialagent (B), and that it does not contain crystal water. However, theantimicrobial agent (C) has the drawbacks that the zirconium or titaniumcompound contained as a metal has a high hardness, the antimicrobialagent (C) tends to bring dirt of a manufacturing machine into the resinin the stage of kneading, and the antimicrobial activity is somewhatlow.

[0022] However, these drawbacks of the antimicrobial agent (C) areresolved by mixing with the above-mentioned antimicrobial agent (B). Theaverage particle diameter of the antimicrobial agent (C) is preferably0.3 to 5 μm, and more preferably 0.5 to 2 μm. If the particle diameteris less than 0.3 μm, the dispersion tends to be poor when theantimicrobial agent (C) is added to the resin. If the particle diameteris more than 5 μm, the mechanical properties of a molded article arelowered.

[0023] The antimicrobial agent (D) used in the present invention is madeof a soluble glass powder containing silver ion. An example of theantimicrobial agent (D) is described in Japanese Laid-Open PatentPublication (Tokkai) No. 3-124810. The antimicrobial agent.(D)advantageously prevents the resin from being discolored and does notcontain crystal water, and has a high degree of freedom in thecomposition ratio. On the other hand, the antimicrobial agent (D) hasthe following drawbacks: The particle shape is non-uniform and thehardness is high, so that the dispersibility is poor and dirt ofmanufacturing machine is easily brought into the resin in the stage ofkneading. However, these drawbacks of the antimicrobial agent (D) areresolved by mixing it with the above-mentioned antimicrobial agent (B).The average particle diameter of the antimicrobial agent (D) ispreferably 0.3 to 10 μm, and more preferably 0:5 to 2 μm. If theparticle diameter is less than 0.3 μm, the dispersion tends to be poorwhen the antimicrobial agent (C) is added to the resin. If the particlediameter is over 10 μm, the mechanical physical properties of the moldedarticle are lowered.

[0024] When the antimicrobial resin composition of the present inventioncomprises the resin (A) and the antimicrobial agents (B) and (C), it ispreferable that 0.01 to 10 parts by weight of the antimicrobial agent(B) and 0.01 to 10 parts by weight of the antimicrobial agent (C) areblended with respect to 100 parts by weight of the resin (A).Preferably, 0.01 to 1 parts by weight of the antimicrobial agent (B) and0.1 to 5 parts by weight of the antimicrobial agent (C) are blended. Ifthe antimicrobial agent (B) is less than 0.01 parts by weight, thedispersibility is hardly improved. On the other hand, if theantimicrobial agent (B) is more than 10 parts by weight, the resin iseasily discolored. If the antimicrobial agent (C) is less than 0.01parts by weight, the antimicrobial properties cannot be exhibited. Onthe other hand, if the antimicrobial agent (C) is more than 10 parts byweight, the dispersion tends to be poor, dirt is brought in when theagent is added to the resin and kneaded, and the resin is discolored byheat.

[0025] When the antimicrobial resin composition of the present inventionconsists of the resin (A) and the antimicrobial agents (B) and (D), itis preferable that 0.01 to 10 parts by weight of antimicrobial agent (B)and 0.01 to 10 parts by weight of antimicrobial agent (D) are blendedwith respect to 100 parts by weight of the resin (A). Preferably, 0.01to 1 parts by weight of antimicrobial agent (B) and 0.01 to 5 parts byweight of antimicrobial agent (D) are blended. If the antimicrobialagent (B) is less than 0.01 parts by weight, the dispersibility ishardly improved. On the other hand, if the antimicrobial agent (B) ismore than 10 parts by weight, the resin is easily discolored. If theantimicrobial agent (D) is less than 0.01 parts by weight, theantimicrobial properties cannot be exhibited. On the other hand, if theantimicrobial agent (D) is more than 10 parts by weight, the dispersiontends to be poor, dirt is brought in when the agent is added to theresin and kneaded, and the resin is discolored by heat.

[0026] In order to further improve the thermostability and the heatmoldability, an antioxidant, an inorganic filler (such as talc, mica,and wallastonite), a heat stabilizer, a photostabilizer, a flameretardant, a plasticizer, an antistat, a releasing agent, a foamingagent, a nucleating agent may be added to the antimicrobial resincomposition of the present invention.

[0027] The antimicrobial resin composition of the present invention canbe obtained in the following manner, for example, when the resin (A) isa thermoplastic resin: the resin (A), the antimicrobial agent (B), theantimicrobial agent (C) or antimicrobial agent (D), and if necessary,additives such as an antioxidant are blended, premixed, and then kneadedby an extruder.

EXAMPLES

[0028] Hereinafter, the present invention will be described in detail byway of examples and comparative examples. However, the present inventionis not limited to these examples.

Examples 1 to 8

[0029] With respect to 100 parts by weight of a polypropylene resin asthe resin (A), four kinds of zeolite of antimicrobial agent “Bactekiller(manufactured by Kanebo LTD.)” that have the silver ion contents (wt %)and average particle sizes shown in table 1 were used as theantimicrobial agent (B), an antimicrobial agent of a zirconium phosphatewas used as the antimicrobial agent (C), and a glass-based antimicrobialagent was used as the antimicrobial agent (D). The antimicrobial agent(B) and the antimicrobial agent (C) or the antimicrobial agent (D) wereblended in the ratio shown in the table 1, and preliminary kneading wasperformed with a Henschel Mixer. The obtained mixture was melt-kneadedwith an extruder (50 mm φ, single screw) and then pelletized. Thetemperature, of the resin in the extruder was 190° C. at the rearsection of the cylinder, 200° C. at the middle section of the cylinder,220° C. at the front section of the cylinder, and 220° C. at the diessection.

[0030] The dispersibility, the discoloration properties, and theantimicrobial properties of the obtained antimicrobial resin composition(pellets) are measured and evaluated by the following method. The table1 shows the results.

[0031] (1) Dispersibility: The resin to which the antimicrobial agenthad been added was subjected to melt-pressing at 250° C. to produce athin film sample. Then, the size of coarse particles of the thin filmsample was measured by a transmission optical microscope and evaluatedas follows.

[0032] favorable: 0 coarse particle with 20 μm or more/mm²

[0033] normal: 1 to 5 coarse particles with 20 μm or more/mm²

[0034] defective: 6 or more coarse particles with 20 μm or more/mm²

[0035] (2) Discoloration resistance: A test of discoloration resistancewas conducted for 25 hours with a testing apparatus for light resistancepromotion (Xenon Weather Meter), and then a color difference ΔE wasmeasured with a color-difference meter. The larger the value of ΔE is,the higher the degree of discoloration is.

[0036] favorable: ΔE of 0.1 or more and less than 0.6

[0037] normal: ΔE of 0.6 or more and less than 1.1

[0038] defective: ΔE of 1.1 or more

[0039] (3) Antimicrobial properties: The antimicrobial properties wereevaluated based on the method defined in a Test for AntimicrobialActivity for antimicrobial products (Society of Industrial-Technologyfor Antimicrobial Articles).

[0040] Test method: Film Adherence Method

[0041] Evaluated bacteria:

[0042]Escherichia coli and Staphylococcus aureus

[0043] Contact time of bacteria and test sample: 24 hours

[0044] Evaluation: bacteria were contacted with a resin molded articleto which the antimicrobial agent was added, and was covered with thefilm. Then, 24 hours later, the number of bacteria was counted.

[0045] favorable: A decreasing rate from the number of inoculatedbacteria of {fraction (1/100)} or more

[0046] normal: A decreasing rate from the number of inoculated bacteriaof {fraction (1/10)} or more and less than {fraction (1/100)}.

[0047] defective: A decreasing rate from the number of inoculatedbacteria of less than {fraction (1/10)}.

Comparative Examples 1 to 7

[0048] The antimicrobial resin compositions were obtained by the sameprocedures as in the Examples 1 to 8 except that the resin (A), and theantimicrobial agents (B), (C), and (D) were blended in the ratio shownin Table 1. Then, their physical properties were measured and evaluatedin the same manner as in the Examples 1 to 8. Table 1 shows the results.TABLE 1 Comparative Examples 1 2 3 4 5 6 7 Composition A PP resin 100100 100 100 100 100 100 B* (Ag: 0.1) 2 μm 1.0 (Ag: 0.1) 5 μm 1.0 (Ag:2.0) 2 μm 1.0 (Ag: 2.0) 5 μm 1.0 C Zirconium- 1.0 phosphate D Glass 10Properties Dispersibility G G G G G U B Color fastness G U G B U G UAntimicrobial B U U G G U G properties Examples 1 2 3 4 5 6 7 8Composition A PP resin 100 100 100 100 100 100 100 100 B* (Ag: 0.1) 2 μm0.5 0.5 (Ag: 0.1) 5 μm 0.5 0.5 (Ag: 2.0) 2 μm 0.5 0.5 (Ag: 2.0) 5 μm 0.50.5 C Zirconium 0.5 0.5 0.5 0.5 phosphate D Glass 0.5 0.5 0.5 0.5Properties Dispersibility G G G G G G G G Color fastness G G G G G G G GAntimicrobial G G G G G G G G properties

[0049] As seen from the comparison between Examples 1 to 8 andComparative Examples 1 to 7 in Table 1, by using the antimicrobialagents (B) and (C) together or using the antimicrobial agents (B) and(D) together, resin compositions having better dispersibility, higherdiscoloration resistance and more excellent antimicrobial properties areobtained than those of the resin compositions obtained by using eachantimicrobial agent alone.

[0050] As described above, the antimicrobial resin composition of thepresent invention has excellent dispersibility, discoloration resistanceand antimicrobial properties by using the specific two kinds ofantimicrobial agents together, and is useful for rendering productsantimicrobial, such as stationery, daily necessities, home electricappliances, building materials, and textile products.

What is claimed is:
 1. A antimicrobial resin composition, wherein aresin (A) is blended with an antimicrobial agent (B) in which at leastone kind of metal ion selected from the group consisting of silver,copper, zinc and tin is supported on zeolite, and an antimicrobial agent(C) that includes a silver ion-containing phosphate as an activeingredient, or a soluble glass powder (D) containing silver ion.
 2. Theantimicrobial resin composition according to claim 1, wherein 0.01 to 10parts by weight of the antimicrobial agent (B) and 0.01 to 10 parts byweight of the antimicrobial agent (C) are blended with respect to 100parts by weight of the resin (A).
 3. The antimicrobial resin compositionaccording to claim 1, wherein 0.01 to 10 parts by weight of theantimicrobial agent (B) and 0.01 to 10 parts by weight of theantimicrobial agent (D) are blended with respect to 100 parts by weightof the resin (A).
 4. The antimicrobial resin composition according toany one of claims 1 to 3, wherein the resin (A) is a thermoplasticresin.
 5. The antimicrobial resin composition according to claim 4,wherein the thermoplastic resin is a polyolefin.
 6. The antimicrobialresin composition according to claim 5, wherein the polyolefin ispolypropylene.